Preconditioning of bone marrow-derived mesenchymal stem cells highly strengthens their potential to promote IL-6-dependent M2b polarization

Abstract

BackgroundDuring the last decade, mesenchymal stem cells (MSCs) have gained much attention in the field of regenerative medicine due to their capacity to differentiate into different cell types and to promote immunosuppressive effects. However, the underlying mechanism of MSC-mediated immunoregulation is not fully understood so far. Macrophages are distinguished in classical activated, pro-inflammatory M1 and alternatively activated M2 cells, which possess different functions and transcriptional profiles with respect to inflammatory responses. As polarization is not fixed, macrophage functional plasticity might be modulated by the microenvironment allowing them to rapidly react to danger signals and maintaining tissue homeostasis.MethodsMurine MSCs were preconditioned with IL-1ß and IFN-ɣ to enhance their immunosuppressive capacity regarding macrophage polarization under M1- and M2a-polarizing conditions. Macrophage polarization was analyzed by real-time PCR, flow cytometry, and cytokine detection in culture supernatants. The role of MSC-derived nitric oxide (NO), prostaglandin E2 (PGE2), and IL-6 in this process has been evaluated using siRNA transfection and IL-6 receptor-deficient macrophages, respectively.ResultsPreconditioned, but not unprimed, MSCs secreted high levels of NO, IL-6, and PGE2. Co-culture with macrophages (M0) in the presence of M1 inducers (LPS + IFN-ɣ) led to significant reduction of CD86 and iNOS protein in macrophages and diminished TNF-α secretion. Additionally, CD86 and iNOS protein expression as well as NO and IL-10 secretion were markedly increased under M2a-polarizing culture conditions (IL-4). MSC-dependent macrophage polarization did not depend on direct cell-cell contact. Co-culturing in the presence of LPS and IFN-ɣ resulted in the upregulation of M2a, M2b, and M2c marker genes, whereas in the presence of IL-4 only M2b markers were significantly increased. In turn, IL-10-producing regulatory M2b cells significantly inhibited IFN-ɣ expression in CD4+ T lymphocytes. Finally, we show that MSC-mediated macrophage polarization strongly depends on IL-6, whereas a minor role for NO and PGE2 was found.ConclusionsPreconditioning of MSCs highly strengthens their capacity to regulate macrophage features and to promote immunosuppression. Repression of M1 polarization during inflammation and M2b polarization under anti-inflammatory conditions strongly depend on functional IL-6 signaling in macrophages. The potential benefit of preconditioned MSCs and IL-6 should be considered for future clinical treatment.Electronic supplementary materialThe online version of this article (10.1186/s13287-018-1039-2) contains supplementary material, which is available to authorized users.

Integrin-specific hydrogels modulate transplanted human bone marrow-derived mesenchymal stem cell survival, engraftment, and reparative activities

“…Co-culture of hMSC-laden GFOGER-functionalized gels and macrophages upregulated macrophage secretion of the cytokine IL-10, a potent anti-inflammatory factor, compared with all other gel conditions. hMSCs have been shown to promote IL-6 dependent macrophage polarization toward an anti-inflammatory IL-10 producing phenotype 50,54 , consistent with the increased hMSC secretion of IL-6 and increased macrophage secretion of IL-10 seen in our experiments. These results indicate that integrinspecific hydrogels alter the hMSC secretome and result in functional differences in hMSC-immune cell interactions.…”

“…hMSC secretion of monocyte recuritment cytokine MCP-1 and IL-6 were also increased in vitro. In agreement with previous studies, IL-6 secreting hMSC promoted macrophage polarization toward an anti-inflammatory IL-10 producing phenotype in vitro 50,54 . The host receptor for MCP-1, CCR2, was also upregulated in GFOGER-presenting hydrogels in vivo.…”

Differential effects of heat-inactivated, secretome-deficient MSC and metabolically active MSC in sepsis and allogenic heart transplantation

“…Recent publications suggest an enhanced immunosuppressive effect of MSCs that were preactivated with TNF‐α, IFN‐γ, or IL‐1β . Interestingly, the improved immunomodulatory effect of preactivated MSCs has to a large extent been attributed to their superior paracrine activity with an increased secretion of immunomodulatory molecules, which does not provide a sufficient explanation for the beneficial effect of secretome‐deficient HI‐MSCs in our sepsis model.…”

Characterization of the immunomodulatory properties of alveolar bone-derived mesenchymal stem cells

“…BMSC secretion of IL-6 has been reported to skew monocyte differentiation from CD14 − CD1a + DCs to CD14 + CD1a − cells (which have a lower immunostimulatory capacity towards anti-inflammatory macrophage differentiation) [51]. Using mouse macrophages lacking α chain of IL-6 receptor, Philipp et al suggested that IL-6 signaling is indispensable for alternative activation of macrophages by BMSC coculture or IL-4 treatment [52]. Therefore, we hypothesized that aBMSCs have immunomodulatory effects on monocytes and macrophages similar to BMSCs.…”